Conventional heat exchangers used in refrigeration-and-air-conditioning apparatuses have employed copper pipes. However, due to high copper price these days, relatively cheaper alternative materials are required. Under the circumstances, a refrigeration-and-air-conditioning apparatus that employs an aluminum heat exchanger made of an aluminum material, instead of a copper material, has been proposed (for example, see Patent Literature 1).
Herein, when, for example, a heat exchanger installed in a refrigeration-and-air-conditioning apparatus is serving as an evaporator, air supplied to the heat exchanger is cooled, and dew condensation water is deposited on fins and heat transfer tubes (refrigerant pipes) of the heat exchanger. Because aluminum heat exchangers have lower anticorrosive capacity than copper heat exchangers, the fins and heat transfer tubes of the heat exchangers are corroded by the dew condensation water. If the heat transfer tubes corrode, a through-hole may be formed.
To suppress this situation, in the technique disclosed in Patent Literature 1, when a refrigeration-and-air-conditioning apparatus employs an aluminum heat exchanger, a sacrificial anode layer formed of zinc (Zn layer) is formed on the surface of the heat transfer tubes. By allowing the sacrificial anode layer to corrode, corrosion of the heat transfer tubes is suppressed.